This event is ironic because both the cat and the pickle dish are symbolic of Zeena Frome, but the breaking of the dish occurs while Mattie and Ethan are having their private dinner on a night when Zeena is away from home. By this point in the novel the reader knows that Ethan is very enamored of Mattie with her youthful innocence and cheery disposition, but he is already married to the hypochondriac, Zeena, and Mattie is only there because Zeena needs help around the house and Mattie has no other family to take her in. Mattie feels a connection with Ethan, but knows that the situation isn't very hopeful for the two of them. On this night though, she prepares a nice dinner and gets out Zeena's very special red pickle dish, a wedding gift. She and Ethan almost seem to be "playing house" this night as they eat their dinner and sit peacefully afterwards, sewing and reading by the fire. When Zeena's cat breaks the pickle dish it is almost as if Zeena is there -- the act breaks the dream-like quality of the evening, and the crash of the dish is like the crashing reality of their situation. It is as if Zeena herself comes through the door to break the mood. It is ironic that Zeena would never have used the dish for a common meal, and it shouldn't have out in the first place, but now Zeena will be suspicious of Ethan and Mattie and what else happened the night she was away.